Scholtz Gerhard
School of Biological Science, University of New South Wales, Kensington, P.O. Box 1, 2033, NSW, Australia.
Rouxs Arch Dev Biol. 1992 Dec;202(1):36-48. doi: 10.1007/BF00364595.
The cell division pattern of the germ band of Cherax destructor is described from gastrulation to segmentation, limb bud formation, and early neurogenesis. The naupliar segments are formed almost simultaneously from scattered ectoderm cells arranged in a V-shaped germ disc, anterior to the blastopore. No specific cell division pattern is recognisable. The post-naupliar segments are formed successively from front to rear. Most post-naupliar material is budded by a ring of about 39 to 46 ectoteloblasts, which are differentiated successively and in situ in front of the telson ectoderm. The ectoteloblasts give rise to 15 descendant cell rows by unequal divisions in an anterior direction, following a mediolateral mitotic wave. Scattered blastoderm cells of non-ectoteloblastic origin in front of the ectoteloblast descendants and behind the mandibular region are also arranged in rows. Despite their different origins, teloblastic and non-teloblastic rows cleave twice by mediolateral mitotic waves to form 4 regular descendant rows each. Thereafter, the resulting grid-like pattern is dissolved by stereotyped differential cleavages. Neuroblasts are formed during these differential cleavages and segmentation becomes visible. Each ectoderm row represents a parasegmental unit. Therefore, the segmental boundary lies within the area covered by the descendants of 1 row. Segmental structures (limbs, ganglia) are composed of derivatives of 2 ectoderm rows. The results are compared with the early development of other crustaceans and insects in relation to mechanisms of germ band formation, segmentation, neurogenesis, and evolution.
本文描述了破坏螯虾胚带从原肠胚形成到分节、肢芽形成和早期神经发生过程中的细胞分裂模式。无节幼体节段几乎同时由排列在胚孔前方呈V形胚盘的分散外胚层细胞形成。未观察到特定的细胞分裂模式。无节幼体后的节段从前向后依次形成。大多数无节幼体后的组织由大约39至46个外胚层端细胞组成的环产生,这些端细胞在尾节外胚层前方依次原位分化。外胚层端细胞通过不等分裂向前产生15个后代细胞列,遵循中外侧有丝分裂波。在外胚层端细胞后代前方和下颌区域后方,非外胚层端细胞起源的分散胚盘细胞也排列成行。尽管它们起源不同,但端细胞和非端细胞列通过中外侧有丝分裂波分裂两次,各自形成4个规则的后代列。此后,通过定型的差异分裂,形成的网格状模式被瓦解。在这些差异分裂过程中形成神经母细胞,分节变得可见。每个外胚层列代表一个副节段单位。因此,节段边界位于1列后代覆盖的区域内。节段结构(肢体、神经节)由2个外胚层列的衍生物组成。将这些结果与其他甲壳类动物和昆虫早期发育过程中胚带形成、分节、神经发生和进化机制进行了比较。